Self-Cleaning Litter Box

ABSTRACT

A self-cleaning litter box ( 50 ) provides various advantages over the prior art. In particular, in one embodiment, the self-cleaning litter box ( 50 ) is configured to use a one piece litter cartridge ( 20 ) having a litter compartment ( 26 ) and a waste compartment  24.  In another embodiment, the cartridge ( 20 ) is non-compartmentalized. In another embodiment, the system includes a rake assembly ( 56 ) configured with a drive assembly ( 58 ) that is protected from waste contamination. In accordance with the invention, the self-cleaning litter box ( 50 ) is configured to be used with all types of litter including crystal type litter.

CROSS REFERENCE TO RELATED APPLICATIONS

This case claims the benefit of US provisional patent application No.60/507,416 filed on Sep. 30, 2003.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a self-cleaning litter box and moreparticularly to a self-cleaning litter box, which, in one embodiment,includes a disposable litter cartridge and an automatic rake assembly.

2. Description of the Prior Art

Various litter boxes are known in the art. Both reusable and disposablelitter boxes are known. Reusable litter boxes are normally formed fromplastic and are configured as a rectangular tray with 3-4 inchsidewalls. Normally, such reusable litter boxes need to be maintaineddaily or every few days. In order to facilitate the care and cleaning oflitter boxes, disposable litter boxes have been developed. Examples ofsuch disposable litter boxes are disclosed in U.S. Pat. Nos.: 4,171,680;4,271,787 and 6,065,429. Such disposable litter boxes normally include adisposable box or tray filled with an absorbent material, commonly knownas kitty litter.

In order to further facilitate the upkeep of such litter boxes,self-cleaning litter boxes have been developed. Commercially availableself-cleaning litter boxes primarily use “clay” or “clumping° littersand require the periodic addition of fresh kitty litter and the removalof waste every few days. Examples of such self-cleaning litter boxes aredisclosed in U.S. Pat. Nos.: 4,574,735; 5,048,465; 5,477,812; 6,082,302;6,378.461; and Re 36,847, hereby incorporated by reference.

U.S. Pat. No. 4,574,735 discloses a self-cleaning litter box whichincludes a generally circular upper chamber, a lower disposablecontainer, and a rotatable rake assembly. The rotatable rake assemblyincludes a plurality of tines that are horizontally oriented andconnected to a centrally located spindle. The spindle, in turn, isdriven by an electric motor by way of a gearing arrangement.Accordingly, when the electric motor is energized, the tines arerotated, thus pushing the solid waste products towards a dischargeopening in the upper chamber that is in communication with the lowerwaste container. Unfortunately, such a configuration is not entirelyefficient since it is known that, not all of the waste is dischargedinto the lower waste container..

In order to solve this problem, self-cleaning litter boxes have beendeveloped which rely on linear motion of a rake assembly to deposit thewaste into a waste compartment, located at one end of the litter box.For example, U.S. Pat. No. 5,048,465 discloses a self-cleaning litterbox which includes a rake assembly, a removable and reusable lifter trayand a disposable or reusable waste receptacle disposed at one end of thereusable litter tray. The rake assembly includes a plurality of tinesused to comb in a linear motion fashion through the litter box. Thetines are pivotally mounted. A stop, mounted at one end of the littertray, causes the tines to rotate and lift the solid waste upwardly andover a wall separating the litter tray and the waste compartment. Oncethe extended end of the tines are rotated above the wall, continuedmotion of the rake assembly causes the extended ends of the tines tolift a lid and drop the solid waste products into the waste compartment.Although the self-cleaning litter box system disclosed in the '465patent facilitates upkeep of the litter box, the litter tray must berefilled often; a cumbersome task. Further, the entire system must beperiodically emptied and disassembled for cleaning; also a cumbersometask. Also, the relative complexity of the device results in the cost ofthe device being, relatively expensive.

U.S. Pat. Nos. 5,477,812; 6,082,302; 6,378,461; and Re. 36,847 alsodisclose self-cleaning litter boxes. Like the ‘465 patent, theself-cleaning litter boxes disclosed in these patents also include areusable litter tray and a disposable waste container.

There are various problems associated with the self-cleaning litterboxes disclosed in the above-mentioned U.S. patents. First, becausethese boxes often require the use of clumping litter, the waste binfills quickly with clumped urine and solid waste. Therefore the wastebin must be emptied every few days or more frequently, especially inmultiple cat applications. Second, removal of the waste container iscumbersome and often requires the user to come in contact with thewaste. Third, fresh kitty litter must be added to the litter tray on anon-going basis. Fourth, the drive assembly in such self-cleaning litterboxes is known to include a drive motor that travels with the rakeassembly in a toothed track that is exposed to the litter area. Bymounting the motor to the rake, electrical power is applied to a movablechassis, thus requiring a take up reel for an electrical cord, which isknown to be inherently risky and prone to failure. When too much litteris used in the litter tray, the motor can be insufficient to drive therake through the litter, thereby causing a jam which requires the ownerto intervene. Conversely, if too little litter is used, or if the catredistributes the litter in a particular way, a clump can cement to thebottom of the litter pan and prevent the rake from passing through thelitter area. In other instances, the cat causes litter to accumulate inthe tracks, also causing damage to the drive system and/or requiringfurther user intervention. Further, the electrical motor is not fullyprotected from urine, and can be damaged by the cat through normaloperation. This motor is also known to be loud if the box is placed inclose proximity to the user. Fifth, known self-cleaning litter boxes arenot suitable for use with crystal litter. In particular, due to theirregular shape of the crystal litter and tendency to pack andinterlock, a wave tends to build up in front of the rake assembly, whichamong other things, may prevent the rake assembly from completing acleaning stroke. Thus, there is a need for a self-cleaning litter boxwhich is) easier to use than known self-cleaning litter boxes; is morereliable; does not expose electrical or mechanical components tocontamination; eliminates the need for a take up reel; and is suitablefor use with non-dumping litters such as crystal litter.

SUMMARY OF THE INVENTION

The present invention relates to a self-cleaning litter box whichprovides various advantages over the prior art. In particular, in oneembodiment, the self-cleaning litter box is configured to use adisposable cartridge that is pre-filled with litter and configured toboth provide litter and contain waste, thus eliminating the need for theuser to dean the litter tray and handle heavy litter supply containers.In other embodiments, the system includes a rake assembly configuredwith a drive assembly that is protected from contamination. Inaccordance with another embodiment of the invention, the self-cleaninglitter box includes a rake assembly which includes a plurality of spacedapart tines that is configured so that all types of litter includingcrystal type litter can be used.

DESCRIPTION OF THE DRAWING

These and other advantages of the present invention will be readilyunderstood with reference to the following specification and attacheddrawing wherein.

FIG. 1 is a perspective view of a rectangular cartridge configured witha litter compartment and a waste compartment in accordance with oneembodiment of the present invention.

FIG. 2 is a perspective view of the self-cleaning litter box inaccordance with one embodiment of the present invention shown with therake assembly in a position opposite the waste storage position.

FIG. 3 is a partial side view of the self-cleaning litter box shown inFIG. 2, illustrating the side rail detail.

FIG. 4 is an exploded perspective view of the drive assembly for usewith the self-cleaning litter box illustrated in FIG. 2.)

FIG. 5A is a top view of the self-cleaning litter box illustrated inFIG. 2, shown with the rake assembly in a position opposite the wastestorage position.

FIG. 5B is a sectional view along lines 5B-5B of FIG. 5A.

FIG. 6A is a top view of the self-cleaning litter box illustrated inFIG. 2, shown with the rake assembly in an intermediate position duringthe cleaning stroke.

FIG. 6B is a sectional view along lines 6B-6B of FIG. 6A.

FIG. 7A is a top view of the self-cleaning litter box illustrated inFIG. 2, shown with the rake assembly in a position at the end of thecleaning stroke.

FIG. 7B is a sectional view along lines 7B-7B of FIG. 7A.

FIG. 8A is a top view of the self-cleaning litter box illustrated inFIG. 2, in accordance with the present invention shown at a positionwhere the rake assembly is lifting the cover on the waste compartment

FIG. 8B is a sectional view along lines 8B-8B of FIG. 8A.

FIG. 9A is a top view of a self-cleaning litter box illustrated in FIG.2, shown with the rake assembly in a dumping position.

FIG. 9B is a sectional view along lines 9B-9B of FIG. 9A.

FIG. 10A is a top view of the self-cleaning litter box illustrated inFIG. 2, shown with the rake assembly at an intermediate position duringthe backstroke.

FIG. 10B is a sectional view along lines 10B-10B of FIG. 10A.

FIG. 11A is a top view of the self-cleaning litter box illustrated inFIG. 2, shown with the rake assembly at the end of its backstroke.

FIG. 11B is a sectional view along lines 11A-11A of FIG. 11A.

FIG. 12 is an exemplary schematic diagram of the control system for theself-cleaning litter box illustrated in FIG. 2.

FIG. 13 is a flow diagram for the control system for the self-cleaninglitter box illustrated in FIG. 2.

FIGS. 14A-14C illustrate an alternate embodiment of a litter cartridgein accordance with the present invention.

FIGS. 15A-15C illustrate another alternative embodiment of a littercartridge in accordance with the present invention.

FIG. 16 is an isometric view of an alternate embodiment of theself-cleaning litter box in accordance with the present invention.

FIG. 17A is another isometric view of the self-cleaning litter boxillustrated in FIG. 16, shown in a use position.

FIG. 17B is a side elevational view of the self-cleaning litter boxillustrated in FIG. 17A.

FIG. 17C is a sectional view along lines 17C-17C of FIG. 17A.

FIG. 17D is a sectional view along lines 17D-17D of FIG. 17Billustrating an exemplary labyrinth seal in accordance with one aspectof the invention.

FIG. 18A is an isometric view of the self-cleaning litter boxillustrated in FIG. 17, shown in a position which enables the littertray to be removed.

FIG. 18B is a sectional view of the litter box in the positionillustrated in FIG. 18A.

FIG. 19 is an exploded isometric view of the self-cleaning litter boxillustrated in

FIG. 16 which illustrates a first embodiment of the drive assembly whichincludes a drive nut and a nut follower.

FIG. 20 is an isometric view of the self-cleaning litter box illustratedin FIG. 16, shown with the top housing removed and the drive assemblyillustrated in FIG. 19.

FIG. 21 is a side view of the self-cleaning litter box with the tophousing removed, illustrated in FIG. 16.

FIG. 22A-C are partial views of the system illustrated in FIG. 21 withthe side rail removed to illustrate elements of the lifting mechanism ofthe system lid

FIG. 23A-D are partial views of the self-cleaning litter box illustratedin FIG. 21 with the side rail removed, illustrating the parking of therake into home position

FIGS. 24A-C are partial views of the self cleaning litter boxillustrated in FIG. 21 which illustrate rake parking in a home positionwith an alternative embodiment of the drive assembly.

FIG. 25 is an electrical schematic diagram for a controller for use withthe embodiment illustrated in FIGS. 16-24 and 27.

FIG. 26 is a logic diagram for the controller illustrated in FIG. 25.

FIG. 27A-D are sectional views illustrating a raking cycle for theself-cleaning litter box in FIG. 16

DETAILED DESCRIPTION

The present invention relates to a self-cleaning litter box. Variousembodiments of the invention are contemplated. One embodiment isillustrated in FIGS. 1-15. A second embodiment is illustrated in FIGS.16-27. In both illustrated embodiments, the self-cleaning litter boxincludes a litter tray, a rake assembly and a drive assembly. The broadprinciples of the invention are applicable to both disposable andreusable litter trays. In the embodiment illustrated in FIGS. 1-15, adisposable litter tray is provided and configured with two compartments:a litter compartment and a waste compartment. The embodiment illustratedin FIGS. 16-27 illustrates an embodiment in which the litter tray mayalso be disposable and not compartmentalized.

First Embodiment

As mentioned above, the first embodiment is illustrated in FIGS. 1-15and includes a litter tray, rake assembly, drive assembly, and acontroller. In that embodiment, a disposable litter tray is providedthat is compartmentalized and includes a litter compartment and a wastecompartment. The waste compartment may be provided with a hinged cover.The rake assembly includes a plurality of tines carried by a movablechassis that is adapted to comb the litter compartment during a cleaningstroke. As the rake assembly completes its cleaning stroke, furthermovement of the rake assembly in the direction toward the wastecompartment causes a lifting arm or lever to lift the cover to enablethe solid waste material to be deposited into the waste compartment. Ina storage position, the rake assembly rests at one end of the litter boxwith the tines below the fill level of the litter to form a compactprofile.

As will be discussed in more detail below, the various embodiments ofthe present invention provide various advantages over the prior as willbe discussed in detail below. First, the self-cleaning litter box may beconfigured for use with a disposable litter tray. Second, the driveassembly for the rake may be configured to be protected fromcontamination. Third, the rake may be configured to be used with alltypes of litter including crystal litter.

Litter Cartridge

In one embodiment of the invention as illustrated In FIG. 1, theself-cleaning litter box is configured to receive a litter cartridge,which may be disposable. However, even though the self-cleaning litterbox 50 is illustrated and described with a disposable litter cartridge20, the principles of the present invention are applicable to reusablelitter trays as well.

FIG. 1 illustrates a compartmentalized litter cartridge which defines alitter compartment and a waste compartment. The litter cartridgeillustrated in FIG. 1 includes a separator wall between the littercompartment and the waste compartment. As such, the litter cartridgeillustrated in FIG. 1 must be used with a rake assembly that can liftthe rake, for example, the rake assembly described and illustrated inconnection with FIGS. 3-13.

The disposable litter cartridge 20 facilitates the upkeep of the litterbox. As shown in FIG. 1A, the disposable litter cartridge, generallyidentified with the reference numeral 20, may be formed as a generallyrectangular tray with a peripheral lip 21 defining a plurality ofsidewalls 30 and a floor 32. A separator wall 22 defines a wastecompartment 24 and a litter compartment 26. Ribs 28 may be formed in thefloor 32 of the litter compartment 24 for extra strength. The wastecompartment 24 may be provided with a hinged cover 34. Various hinges 36are suitable for this application. For example, the hinge 36 may be aliving hinge or other type of hinge. The type of hinge is not critical.The cover 34 is hinged on one end of 38 of the tray.

The cartridge 20, as well as the cartridge 206 described below,may beformed from various plastic materials, such as polyethyleneterephthalate (PET) or polypropylene and formed by Injection molding orvacuum formed. The cartridge 20 may be made from other materials, suchas cardboard, and lined with a plastic liner, for example.

The cartridge 20 Is dimensioned to be received within the self-cleaninglitter box illustrated in FIGS. 2-10. Registration features may beincorporated into the disposable cartridge 20 as well as the litter boxto prevent unapproved litter cartridges from being installed in thelitter box as well as preventing the cartridge from being installedimproperly. For example, one or more spaced apart transverse slots (notshown) may be formed in bottom of the tray. The spaced apart slots maybe configured to receive) the bars extending across the litter box.Other registration methods are also contemplated.

In a shelf position, in one embodiment of the invention, the cartridge20 contains litter up to a fill line 40 and sealed with a removablecover (not shown) and sealed to the lip 21. The cover 34 over the wastecompartment may be initially sealed by way of an adhesive applied to thelip 21 as well.

Replacement of a cartridge 20 is as simple as removing the old cartridgeand replacing it with a new cartridge. Such a configuration providesmany benefits relative to known systems. First, the configurationeliminates the need to handle relatively heavy litter supply containers.Second, since the cartridge 20 is disposable, there is no need to cleanthe tray. Third, the user is not exposed to a dust cloud that isnormally created when the litter is poured into a litter tray.

FIGS. 14A-14C and FIGS. 15A-15C illustrate exemplary alternativeembodiments of the disposable cartridge 20 illustrated in FIG. 1. Theseexemplary embodiments are configured to minimize retail shelf space. Thefirst alternate embodiment is illustrated in FIGS. 14A-14C andidentified with the reference numeral 100 and includes a generallyrectangular tray configured with one or more fold lines 102 to enablethe tray 100 to be folded in halves or thirds. The second alternateembodiment illustrated in FIGS. 15A-15C, generally identified with thereference numeral 104, may include a single fold line 106 defining twocompartments 108 and 110. One of the two compartments may be configuredwith accordion type folds as shown in FIG. 15B to enable the tray to becompressed as shown in FIG. 15A.

Another alternate embodiment of the litter cartridge is illustrated inFIG. 19. In this embodiment, the litter tray is formed as a generallyrectangular tray that is not compartmentalized, which may be disposable.The tray may have a small lid at one end to cover the waste and may havea larger cover to enclose the entire tray for shipment. An importantaspect of the non-compartmentalized litter cartridge is that itsimplifies the drive assembly and the rake assembly. More particularly,the litter cartridge illustrated in FIG. 19 does not include a separatorwall. As such the rake assembly can stay at one level (i.e. travel in asingle horizontal plane) during all operational modes since the rakeassembly does not have to be lifted over a separator wall. As such, thelitter cartridge illustrated in FIG. 19 may be used with the driveassembly illustrated in FIGS. 19-24. With a rake assembly that stays atone level, the mechanism driving the rake assembly is simplified,improving reliability and reducing cost.

An additional benefit of the non-compartmentalized litter tray is thatthe waste is always in contact with the litter. As such, the odor isreduced and drying of the waste is optimized. The solid waste is notremoved from the litter as is commonly done with other litter boxes.

In an off-the-shelf position, the litter tray may contain litter, whichmay be crystal or otherwise, and enclosed with a removable covermaterial, such as shrink wrap or the like. The tray 206 may be placed inuse by removing the removable cover and lowering the self-cleaninglitter box 200 over the litter tray 206, as generally shown in FIGS. 17Aand 18A.

Self-Cleaning Litter Box

The self-cleaning litter box in accordance with the present invention isillustrated in FIG. 2 and generally identified with the referencenumeral 50. The self-cleaning litter box may be used with or without adisposable litter cartridge 20. The self-cleaning litter box 50 mayinclude a pair of spaced apart side rails 52 and 54, a rake assembly 56and a drive assembly 58. One or more rods 61 may be used to connect theside rails 52 and 54 together.

The rake assembly 56 includes a number of tines 64 that are used to combthrough the litter in the litter compartment 26 of the litter tray ordisposable litter cartridge 20, 100 or 104. The tines 64 are angledbackward with respect to the motion direction of the raking assembly andare carried by a chassis or bridge 66, transversely disposed above thelitter box 50. The chassis 66 carries a plurality of spaced apart tines64 and is supported by a pair of spaced apart side plates 68 and 70.

The drive assembly 58 may include a drive motor 71, for example, areversible electrical motor (FIG. 4) and a drive assembly. Various driveassemblies are suitable. For example, the drive assembly may include apair of spaced apart lead screws 72 and 74, driven by the drive motor71. As best shown in FIGS. 2 and 3, the lead screws 72 and 74 may bedisposed in elongated slots in the side rails 52 and 54. A pair ofextending shafts 76 and 78 are coupled to the drive motor 71 by way of apair of couplings 80 and 82. The extended ends of the shafts 76 and 78may be attached to worm gear assemblies 84 and 86, which, in turn, areused to drive the lead screws 72 and 74. The worm gear reduction may be,for example, 20:1 which, in combination with a small pitched lead screw(M6-1.0 thread) allows for a high reduction ratio between the high speedelectric motor and the slow moving rake without the need for a motorgear head. The rake side plates 68 and 70 may be pivotally connected tothe lead screws 72 and 74 by way of a pair of nuts 88 (FIG. 3). Thus, asthe lead screws 72 and 74 are rotated by the electrical motor 71, thenuts 88 are advanced along the lead screws 72 and 74, thus advancing therake assembly 56. Other drive assemblies are suitable for use with thepresent invention, such as drive belt, pneumatic cylinder or the like.

The height and angle of the tines 64 is automatically controlled by theshape of a pair of upper and lower slots 90 and 92 (FIG. 3) formed inthe side rails 52 and 54, which define tracks. In particular, guides orrollers (not shown) may be coupled to the side plates 68. The guides areconnected to a mounting hole 69 (FIG. 3) formed in the rake side plates68 and 70. Each guide is configured to either slide or roll in one ofthe tracks 90, 92 formed in the side rails 52 and 54.

The lower track 92 causes the tines 64 to be in a cleaning positionduring a cleaning stroke as shown in FIG. 5B, while the upper track 90causes the tines to be in a transport position during a back stroke asshown for example in FIG. 10B. After the cleaning stroke, the rollersand thus the rake assembly 56 transitions from the lower track 92 to theupper track 90. In order to prevent the rollers from returning to thelower track 92, a spring loaded pawl 93 may be provided. The springloaded pawl 93 pivots clockwise to allow the roller to transition fromthe lower track 92 to the upper track 90. Continued forward motion ofthe roller by the drive motor 71 causes the rollers and the rakeassembly 56 to move to the left (FIG. 3) to a point 100 where the solidwaste is deposited in the waste compartment 24.

A pair of microswitches 94 and 98 may be used to reverse the directionof the electrical motor 71. In particular, after the solid waste isdumped into the waste compartment 24, a first microswitch 94, locatedadjacent the left end (FIG. 3) of the lower track 92 is tripped by therake assembly 56. This action causes the drive motor 71 and thus therake assembly 56 to reverse directions. In particular, after the firstmicroswitch 94 is tripped, the rake assembly 56 travels to the right(FIG. 3). As the rake assembly 56 trips a second microswitch 95, locatedadjacent to the right end (FIG. 3) of the lower track 92, the directionof the drive motor 71 is again reversed so that the rake assembly 56will travel to the left (FIG. 3) during a cleaning stroke.

As shown in FIG. 5B, a lever or lift arm 102 may be provided. The liftarm 102 is rigidly attached to the one of the rake side plates 68, 70.Thus, as the roller on the rake assembly 56 transitions from the lowertrack 92 to the upper track 90, the lift arm 102 is raised asillustrated in FIG. 8B, which raises the lift arm 34 over the wastecompartment) 24 of the cartridge 20 to enable solid waste to bedeposited in the waste compartment 34 of a disposable litter cartridge.

As shown in FIG. 2, an optical sensor, for example, an infrared emitter108 and an infrared detector 110 may be provided to sense the presenceof a cat in the litter box 50. The infrared emitter 108 may be coupledto one side rail 54, while the infrared detector 110 may be carried bythe opposing side rail 56. The status of the infrared detector 110 iscontinuously monitored as will be discussed in more detail below. Duringnormal operation, an infrared beam is continuously sensed by theinfrared detector sensor 110. When the infrared beam is interrupted, thesystem assumes that a cat is in the litter box 50. After the beam isrestored (i.e., sensor 110 detects the beam once again), the systeminitiates a cleaning cycle, after a predetermined time period, which maybe selectable by the user, for example, 5 minutes or more.

Referring to FIGS. 4 and 12, the exemplary drive assembly 58 includes anelectronics board 114 (FIG. 4). The electronics board 114 is used tocontrol the drive motor 71 as well as the infrared emitter 108 andinfrared detector 110. Referring to FIG. 12, the electronics board 114includes a microprocessor 116, for example, an eight bitmicrocontroller, for example, an Atmel eight bit ADR microcontroller,model no. ATTINY 26L-SC. The power for the microcontroller 116 isprovided by a power supply 120, for example, model no. LM340T-5.0-HTOP,as manufactured by National Semiconductor. The power supply 120 providesa +5 volt DC supply that is connected to the VCC/AVCC pins of themicrocontroller 116. A bypass capacitor C3 is coupled between theVCC/AVCC pins and ground to stabilize the voltage applied thereto. Inparticular, a conventional 120 VAC power supply from a receptacle (notshown) may be applied to a power jack 117. The 120 VAC supply, in turn,may be applied to the power supply 120 by way of a switch, for example,a single pole double throw switch S1, coupled in series with a diode D2which provides half wave rectification of the 120 VAC input supplyvoltage. The half wave rectified power supply voltage is applied to theinput of the power supply 120 which provides a regulated +5 volt DCoutput. A pair of bypass capacitors C2 and C4 may be coupled across theinput and output pins VIN and VO, respectively, and ground to stabilizethe voltage applied thereto.

The +5 volt power supply 120 is also used to drive the infrared emitter108. In particular, the infrared emitter 108 is coupled to the +5 voltpower supply 120 by way of current limiting resister R13. The cathode ofthe infrared emitter 108 is connected to ground by way of a transistorQ2. The base of the transistor Q2 is connected to port PB5 of themicrocontroller 116. Normally, the infrared emitter 108 is oncontinuously. Thus, the transistor Q2 will be continuously turned on byport PB5.

The infrared detector 110 continuously monitors the infrared beam fromthe infrared emitter 108. The infrared detector 110 may be implementedas a phototransistor Q1. The phototransistor Q1 is coupled between the+5 volt power supply 120 and system ground by way of a current limitingresistor R4. The collector of the phototransistor Q1 is coupled to thenon-inverting Input of a comparator 121 by way of a coupling capacitorC1. The non-inverting input of the comparator 121 is referenced to apredetermined voltage by way of the +5 volt DC source and a voltagedivider, formed from a pair of resistors R6 and R7; As shown, thenon-inverting input of the comparator 121 is referenced to +2.5 voltsDC. The inverting input of the comparator 121 is referenced to areference voltage, developed by a plurality of voltage divider resistorsR10, R11 and R12 and the +5 volt DC supply. As shown, the referencevoltage is 10/21 of +5 volts DC or 2.38 volts DC. The output of thecomparator 121 is pulled up to +5 volts DC by way of a pull up resistorR14. Normally, when an infrared beam from the IR emitter 108 is detectedby the IR detector (i.e. phototransistor Q1), the phototransistor Q1conducts, thus connecting the non-inverting input of the comparator 121to ground. A ground applied to the non-inverting input of the comparator121 causes its output to be low, which, in turn, is read at port PB3 ofthe microcontroller 116. When the IR beam is broken, the phototransistorQ1 stops conducting resulting in the non-inverting input of thecomparator 121 being pulled up to +2.5 volts DC by way of the pull upresistor 24. The +2.5 volt DC applied to the non-inverting input of acomparator will be greater than the +2.38 volt DC reference voltageapplied to the non-inverting input, thus causing the output of thecomparator 121 to go high, which is also read by the microcontroller 116at port PB3.

It is assumed that any time the infrared beam is broken that a cat hasentered the litter box. The microcontroller 116 thus initiates a timedelay before initiating an automatic cleaning stroke. As shown, the timedelay may be user selectable. For example, a switch, S3 may be provided.The switch S3 may be a single pole, single throw momentary push buttonswitch. The microcontroller 116 may be programmed to count the number oftimes that the push button switch is depressed. For example, three userselectable time delays-may be provided. The switch S3 is coupled to portPA0 on the microcontroller 116. This port PA0 is normally maintained ata voltage generated by the voltage divider formed by a pair of resistorsR16 and R15, which, in turn, is connected to the output of the half waverectifier diode D2, identified as HV_IN. As shown, about 1/10 of thevoltage HV_IN is applied to the port PA0 of the microcontroller 116 whenthe switch S3 is open. When the switch S3 is closed, the voltage at theport PA0 is coupled to ground. Thus, each time the switch S3 isdepressed, the microcontroller 116 senses a pulse at port PA0. As shown,three exemplary time delays are provided: five minutes; twenty minutes;and one hour. Thus, the switch S3 may be used to select a time delay forinitiating an automatic cleaning cycle after the infrared beam is broke.For example, depressing the switch S3 once may be read as a five minutedelay, while two depressions of the switch S3 may be read as a twentyminute delay. Finally, three depressions of the switch S3 may be used toindicate a one hour time delay. In order to allow the user to know whichtime delay has been selected, a plurality of red LEDs D3, D4, and D5 maybe provided. These LEDs D3, D4, and D5 are connected to ports PA1, PA2,and PA3 of the microcontroller 116 by way of a plurality of currentlimiting resistors R17, R20 and R22, respectively and to the five voltsupply. Thus, the user, can depress the switch S3 and watch the LEDs D3,D4, and D5 until the desired time delay has been selected.

The drive motor 71 (FIG. 4) is driven by four power FETs Q5, Q6, Q7 andQ8. The voltage available at the output of the half wave rectifier D2,identified as HV_IN, is applied to the source terminals of the powertransistors Q5 and Q7 which are normally off. The drain terminals of thepower transistors Q5 and Q7 are tied to the drain terminals of the powertransistors Q6 and Q8 which are normally on. The drain terminals of thepower transistors Q5 and Q7 are also applied to a motor output jack 123which are used to connect to the drive motor 71.

The gate terminals G for the normally off transistors Q5 and Q7 aredriven by the half wave rectified voltage for HV_IN by way of a pair ofresistors R29 and R33. The resistors R29 and R33, in turn, are seriallycoupled to a pair of collector resistors R24 and R34, respectively. Thecollector resistors R24 and R34, in turn, are coupled to the collectorsof a pair of transistors Q3 and Q4 whose emitters are coupled to ground.The bases of the transistors Q3 and Q4 are driven by OUT_H1_1 andOUT_H1_2 signals, available at ports PA4 and PA5 of the microcontrollerby way of current limiting resistors R23 and R26 respectively.

Zener diodes D7 and D8 are connected in parallel with the resistors R29and R33, respectively. These Zener diodes D7 and D8 are used to limitthe voltage applied to the collectors of the transistors Q5 and Q4 to,for example, 10 volts.

The gates of the normally off transistors Q6 and Q8 are driven bysignals OUT_LO_1 and OUT_LO_2, available at the output of ports PA6 andPA7 of the microcontroller 116. The ports PA6 and PA7 are normallypulled down by pull down resistors R18 and R19.

The serial combination of transistors Q5 and Q6 are used to drive thedrive motor 71 in one direction while the serial combination of thetransistors Q7 and Q8 are used to drive the drive motor 71 in a reversedirection. The limit switches 94 and 95, are normally pulled up to +5volts DC by way of pull up resistors R1 and R2 and applied to ports PB0and PB1 of the microcontroller 116. The limit switches 94 and 95 may beprovided with normally open contacts. Thus, when either limit switch isclosed, a +5 volts DC is applied to the ports PB0 and PB1. When, forexample, the limit switch 94 is closed indicating that the rake assembly56 is at one end of the litter box 50, the port PB0 is driven low. Thelow output is sensed by the microcontroller 116, which, for example,generates the signals OUT_H1_1 and OUT_L0_1 signals to cause thetransistors Q5 and Q6 to conduct. During this condition, the transistorsQ7 and Q8 are non-conducting. The rake assembly 56 is driven along thelitter box 50 until the other microswitch 95 is tripped. When themicroswitch 95 is tripped, the transistors Q7 and Q8 are used to drivethe drive motor 71 by way of the signals OUT_H1_2 and OUT_L0_2.

Irrespective of the direction of rotation of the electrical motor 71,the current therethrough is sensed by a plurality of current senseresistors R35-R42. These current sense resistors R35-R42 form a voltagedivider with a resistor R32, which, in turn, is connected to aninverting input of a comparator 127. A capacitor C5 is also coupledbetween the inverting input and ground to stabilize the voltage acrossthe inverting input. A reference voltage is applied to the non-invertinginput of the comparator 127. The reference voltage is developed by the+5 volt DC source and a voltage divider formed by a plurality ofresistors R25, R27 and R28. The output of the comparator 127 is pulledhigh by way of a pull up resistor R21. Thus, the output of thecomparator 127 is normally high and sensed by port PB6 of themicrocontroller 116. Whenever, the current through the current senseresistors exceeds a predetermined value, for example, 1.9 amperes, theoutput of the comparator 127 goes low indicating a locked rotorcondition for a predetermined period of time indicative, for example, ofthe rake assembly 56 being stuck against an obstacle such as a cat.

As mentioned above, the tines 64 rest below the litter level. Inembodiments configured for a disposable litter tray 20, a push buttonS3, for example, a momentary, single pole, single throw push button maybe provided. The push button 53 is pulled high by a pull up resistor R9and sensed by port PB5 of the microcontroller 116. Any time the pushbutton S2 is depressed, the system automatically causes the rakeassembly 56 to move out of the way to facilitate removal of the olddisposable tray and insertion of a new disposable tray. A limit switch129 may be provided at one of the litter box 50. The limit switch 129may be a momentary, single pole, single throw switch. The limit switch129 is pulled high by a pull up resistor R3 and sensed by port PB2 ofthe microcontroller 116. The limit switch 129 is used to cause the rakeassembly 56 to return to a home position after a new disposable littercartridge has been inserted.

FIG. 13 is an exemplary diagram of the control logic for controlling thedrive assembly 58. Initially, the system continuously loops and checkswhether the infrared beam is broken between the infrared emitter 108 andinfrared detector 110 in step 130. The system loops in this state untilthe beam is broken. Once the infrared beam is broken, a timer 1 isstarted in step 132. The system again checks in step 134 to determine ifthe infrared beam is broken. If not, the system loops back the step 130.If the timer has timed out, as indicated in step 136, the system assumesthat a cat is in the box in step 138. If not, the system loops back tostep. 134 and continuously checks whether the infrared beam is broken.Once it is determined that the timer one has timed out and a cat is inthe box, the system checks in step 140 to determine if the infrared beamis broken again. If so, the system loops back to step 138. If not, thesystem assumes that the cat has left the box and initiates a timer 2 instep 142. As discussed above, the system initiates a user selectabletime out period, identified herein as “CLEAN DELAY”. Once the time outperiod of the CLEAN DELAY is complete, as indicated in step 144, thesystem initiates a cleaning stroke in step 146. If not, the system loopsback to step 145. The system continuously checks in step 148 todetermine whether the cleaning stroke is complete by checking theposition of the limit switch 94 in step 148. Once the cleaning cycle iscomplete, the system stops the drive motor 71 in step 150. After thedrive motor 71 is stopped its direction is reversed in step 152. Thedrive motor 71 runs in reverse until the system detects that thecartridge change limit switch 129 has been tripped in step 154. Thecartridge change limit switch 129 is disposed at a location between thelimit switches 94 and 95. When the cartridge change mode has not beeninitiated as determined in step 156, the drive motor 71 is continued tobe run in reverse as indicated in step 158 until the limit switch 95 istripped. When the limit switch 95 is tripped as determined in step 160,the drive motor 71 is stopped in step 162. After the cleaning cycle iscomplete, the system loops back to step 130.

As mentioned above, the system includes a switch S2 (FIG. 12) used toreposition the rake assembly 56 to facilitate removal of the disposablecartridge 20. As such, the system checks in step 164 to determinewhether the cartridge removal switch S2 has been depressed. If so, achange mode flag is set in step 166. Once the change mode flag is set,the rake assembly 56 is cycled through a cleaning stroke in steps146-150. During a cleaning stroke, the rake assembly 56 is guided by thelower track 92 (FIG. 3) in the siderails 52. In order to raise the rakeassembly 56, the direction of the drive motor is reversed in step 152 toposition the rake assembly 56 in the upper track 90, thus raising thetines 64 upwardly. The rake assembly 56 continues in a reverse directionuntil the cartridge change limit switch 129 is tripped, as determined instep 156. Once the limit switch 129 is tripped, the drive motor 71 isstopped in step 168 to enable the user to replace the disposablecartridge 20 (FIG. 1). The system then waits in step 170 until thecartridge change switch S2 (FIG. 12) is again depressed which causes thesystem to return the rake assembly 56 to a home position. In particular,the system repeats steps 158-162.

As mentioned above, the time delay for initiating a cleaning cycle maybe user selectable. As such, the system checks in step 172 to determineif the time delay selection switch S3 (FIG. 12) has been depressed. Ifso, the selected time delay is acknowledged by the system in step 174and the appropriate LED is updated in step 176. If it is determined instep 144 that the second timer has not timed out, the system checks instep 150 to determine if the infrared beam is broken. If so, the systemloops back to step 138 and assumes that a cat is again in the litterbox. If not, the system loops back to step 144 and awaits time out ofthe 60 second timer.

FIGS. 5-11 illustrate the various positions of the rake assembly 56. Forexample, FIGS. 5A and 5B illustrate the position of the rake assembly 56at a position at the beginning of the cleaning stroke. FIGS. 6A and 6Billustrate an intermediate position of the rake assembly 56 during thecleaning stroke. FIGS. 7A and 7B illustrate the end of the cleaningstroke. FIGS. 8A and 8B illustrate a position in which the lifting arm102 lifts the cover 34 over the waste compartment 24. FIGS. 9A and 9Billustrate a dumping position in which the extending ends of the tines64 are disposed within the waste compartment 24 of the litter cartridge20. In this position, solid waste materials as well as clumped littercollected by the tines 64 are deposited into the waste compartment 24.After the dumping position the drive assembly 58 returns to the positionas shown in FIG. 8B. The rake assembly 56 then returns to the far end ofthe litter box 50 with the tines 64 and lift arm 112 raised defining anintermediate backstroke position shown in FIGS. 10A and 10B. FIGS. 11Aand 11B illustrate the position of the rake assembly 56 at the end ofthe backstroke position.

Tine Configuration

In one embodiment of the invention, the configuration of the tines 64allows the litter box 50 to be used with crystal litter as well asclumping litter. In particular, the configuration of the tines 64 allowsthe rake assembly 56 to move through the crystal litter with a minimumwave and thus electrical power. In particular, the configuration of thetines 64 provides a wedge action as the tines 64 move through thecrystal litter, lifting the litter up and allowing it to fall backthrough the tines 64 as the rake assembly 56 moves forward. The tineconfiguration also supports recirculation of the litter to redistributethe litter thus enabling more effective wicking away of liquid waste andmoisture.

Each tine 64 may be formed from cylindrical steel wire, for example 16AWG, which has a much higher stiffness than plastic and further allowsthe use of smaller diameter cross sections, that is critical to reducingdrag through the crystal litter. The round cross section also has a muchsmaller surface area than a more aerodynamic shape which facilitatesmoving through crystal litter. Also each pair of tines 64 may be made upof a single piece of wire bent into a U-shape. The U-shape eliminatessharp ends on the rake proving rounded, smooth ends that protect theuser and cat. In addition, the tines 64 are formed to be flexible whichreduces drag by causing the tines to flex as it moves through thecrystal litter. During a cleaning stroke, the tines 64 flex back andforth and side to side to facilitate movement through crystal litter.Moreover, as best shown, for example in FIG. 5B, the rake tines areformed with two legs 104 and 106. The leg 106 is bent between 10° and60° relative to the straight leg 104, preferably 45°. Alternatively, therake tines can have one leg 106, in which case the tine angle is between10° and 60°, preferably 45°. In both cases, the rake tine angle istipped back with respect to the direction of travel of the rake assembly

The spacing between each of the tines 64 may be 3-20 mm. In particular,each pair of tines 64 may be formed by bending a length of wire into aU-shape having a bend radius of 1 to 5 mm, with two extending tinesspaced 10 mm apart, preferable for crystal litter particles that are 4-5mm in size. Each U-shaped pair of tines is spaced 10 mm from an adjacentU-shaped pair of tines. The spacing between the tines is selected as afunction of the maximum particle size of the litter, both for crystaland non-crystal litter types. For example, the spacing between the tinesmay be selected to be slightly larger than the maximum particle size ofthe litter to some multiple of the maximum particle size of the litter.A given sample of litter will have a distribution of particle sizes,with a defined maximum. In sizing the tine spacing with respect to thelitter particle size, a balance is achieved which allows the rake topass through the litter easily yet still allow the rake to redistributeand mix the litter after a cat has disturbed the litter bed by diggingand piling the litter non-uniformly. If the tine spacing is too smallwith respect to the litter particle size, the rake cannot easily flowtrough the litter and excessive plowing occurs. The same problem resultsif the rake back angle is too small for a given tine spacing and litterparticle size. However, if the rake tine spacing is too large, then therake does not adequately capture and remove solid cat waste. Also, ifthe tine spacing is too large with respect to the litter size, then thelitter is not adequately redistributed after being disturbed by a cat.Through appropriate election of tine spacing and tine back-angle,various size litters can be accommodated. For example, for crystallitter with a particle size distribution of 2-5 mm, a tine spacing ofapproximately 10 mm and a back-angle of 45° achieves good mixing andredistribution, permits rake travel through the litter with lowelectrical power and with limited wave and plowing of the litter to oneside of the bed, and permits the rake to capture and remove all or mostof the solid cat waste deposited into the litter bed.

Contamination Protection

In accordance with an important aspect of the invention, a portion ofthe drive assembly 58, including the electric motor 71, extending shafts76, 78, couplings 80, 82 and worm gear assemblies 84 and 86 is mountedstationary in a separate housing 61 (FIG. 2) adjacent one end of theself-cleaning litter box 50. Such a configuration protects this portionof the drive assembly 58 from contamination. In addition, as discussedabove, the lead screws 72 and 74 are disposed in slots 90 and 92 in theside rails 52 and 54. Although not shown, the slots 90 and 92 arecovered with either a plastic roof extending over the side rail or aside cover that completely shields the drive assembly 58 by way of alabyrinth seal. In an alternate embodiment of the drive mechanism shownin FIGS. 19-24, a top housing provides a labyrinth seal, generallyidentified with the reference numeral 201, along the full length oftravel of the rake assembly, protecting all drive elements fromcontamination by litter and waste. This is best shown in FIG. 17D.

In addition, as best shown in FIG. 3, the micro-switches 94 and 95 aredisposed in cavities 97 and 99 in the &de rails 52 and 54 as discussedabove. As such, unlike known self-cleaning litter boxes, the driveassembly 58 in accordance with the present invention is protected fromcontamination.

Alternative Embodiment

An alternative embodiment of the self-cleaning litter box in accordancewith the present invention is illustrated in FIGS. 16-27 and identifiedwith the reference numeral 200. As shown, the self-cleaning litter box200 includes a top housing 202, a pivotally-mounted system lid 204 and alitter tray 206. As will be discussed in more detail below, the littertray 206 may be disposable and non-compartmentalized.

In accordance with one aspect of the alternative embodiment of presentinvention, the litter tray 206, which may be disposable, forms thebottom floor of the self-cleaning litter box 200 without any mechanicalcoupling thereto. Such a configuration greatly facilitates removal andreinsertion of the litter tray 206 into the self-cleaning litter box200. More particularly, as best shown in FIGS. 17A and 18A, theself-cleaning litter box 200 sits on the floor and surrounds the littertray 206. Thus, in order to remove the litter tray 206, theself-cleaning litter box 200 is simply lifted upwardly, for example, asillustrated in FIGS. 18A and 18B, for example, about an axis 208 (FIG.16). Alternatively, the self-cleaning litter box 200 may be liftedstraight up. Such a configuration also helps maintain cleanliness of thelitter box in that the litter box is above the litter tray and can havesurfaces extend over the edges of the tray so that all waste, scatteredlitter, or misdirected cat urine is directed back into the tray.Vertical removal of a tray would not allow overhanging surfaces, wouldrequire the rake to have a motorized park position and would requiremore cumbersome user actions to grab the lip of the cartridges forvertical removal. Side removal of the tray would require a larger workarea and floor space for cartridge removal Thus, lifting the litter boxas illustrated in FIGS. 18A and 18B is advantageous.

In one embodiment of the invention, as shown in FIG. 16, one panel 210of the housing 202 may be formed with a pair of spaced-apart feet 212and 214. These spaced-apart feet 212, 214 are configured so that theself-cleaning litter box 200 is supported in a vertical position (i.e.,212 and 214 squarely on the ground) as generally shown in FIGS. 18A and18B. Since the litter tray 206 is not mechanically coupled to theself-cleaning litter box 200 and simply sits on the floor, once theself-cleaning litter box 200 Is lifted or placed on end, as shown inFIGS. 18A and 18B, the litter tray 206 may simply be removed andreplaced with a new litter tray 206. After a new litter tray 206 isplaced on the floor, the self-cleaning litter box 200 is then placed ina position on the floor such that the outer housing 202 surrounds thelitter tray 206, as generally shown in FIGS. 17A-17C.

By removing the litter cartridge as described above, the rake assemblydoes not have to be removed from the litter area by motorized means to apark position out of the litter as In the embodiment illustrated inFIGS. 1-15.

In the embodiment illustrated in FIGS. 16-24, the rake tines may remainin the litter at all times at one level in the home position, allowing asimplification of the drive mechanism and controller that controls therake assembly. Furthermore, the user actions required to remove thecartridge are simplified, as the user does not have to command the raketo travel into and out of a park position that is distinct from thenormal home position.

Turning to FIG. 19, an exploded perspective view of the self-cleaninglitter box 200 along with the litter tray 206 is illustrated. Theself-cleaning litter box 200 includes the top housing 202, a chassisassembly 216, a drive assembly 218, a lift arm 220, a system lid 204 arake assembly 222; and a controller 310 (FIG. 32). The drive assembly218 is used to drive the rake assembly 222 from a home position 224 FIG.20) adjacent the end panel 210 (FIG. 16) to a waste position 232 (FIG.20), adjacent the system lid 204. In particular, as will be discussed inmore detail below, the rake assembly 222 (FIG. 19) is periodicallycycled. During a forward stroke in the direction of the arrow 226 (FIGS.27A and 27B), from the home position 224 toward the waste position 232,the rake assembly 222 is configured to be at a negative angle ⊖ relativeto the vertical to permit raking through large particle size litter andto minimize the drag on the rake assembly 222 during a forward stroke.As the rake assembly 222 advances during a forward stroke, solid wastein the litter is raked toward the waste position 232.

As the rake assembly 222 advances towards the waste position 232, thedrive assembly 218 engages the lift arm 220 causing the system lid 204to rotate upward (FIGS. 22A-22C, 27A and 27B). On a return stroke, asindicated by the arrow 234 (FIGS. 27C and 27D), the drive assembly 218reverses direction, as discussed below, causing the rake assembly 222 toflip (I.e. rotate in a counterclockwise direction) so that the rakeassembly 222 is at a positive angle 0 with respect to the vertical axis.

In accordance with one aspect of the invention, the litter cartridge 206may be provided with a tray lid 228 (FIG. 19). More particularly, thelitter cartridge 206 defines a waste end 232 that may be provided with ahinged cover 228. The hinged cover 228 is used to cover the wastematerial, providing improved odor control, protection of the litter boxsystem lid from contamination, and providing a clean area for the userto grab the cartridge upon removal for disposal. As discussed below, thecover 228 may be formed with a living hinge and include a magneticallyattractive plate 236 or formed from magnetically attractive materialthat cooperates with the one or more magnets disposed on the undersideof the system lid 204. The tray may also be provided with a large coverwhich covers the entire surface of the tray. This cover contains litterduring shipment, stiffens the cartridge for easy handling, andfacilities disposal of a used cartridge.

The system lid 204 and the tray lid 228 may be magnetically coupledtogether so that when the system lid 204 rotates upward, the tray lid228 likewise rotates upward. Alternatively, various mechanical couplingmethods are contemplated for coupling the system lid 204 and the traylid 228. For example, a loop of elastic cord secured on one end to thetray lid 228 can be looped over an extending pin (not shown) formed inthe system lid 204 by the user. Various other means may also be used tocouple the system lid 204 and the tray lid 228, such as clips, tapes,latches and the like.

The magnetic coupling allows the self-cleaning litter box 200 to bequickly and easily decoupled and separated from the litter tray 206. Inparticular, the system lid 204 may be provided with a magnet 207 (FIG.27C) on its underside. The tray lid 228 may be provided with a magneticmaterial 236 and positioned to be aligned with one or more magnetscarried by the system lid 204 when the litter tray 206 is registeredwithin the self-cleaning litter box 200. As such, when the system lid204 rotates upwardly, the magnetic attraction will cause the tray lid228 to rotate in the same direction. The strength of the magnet 207 issized so that the system lid 204 is easily magnetically decoupled fromthe tray lid 228 when the self-cleaning litter box 200 is being pickedup or tilted so that the litter tray 206 can be easily removed andreplaced.

After the system lid 204 and corresponding tray lid 228 on the littertray 206 are rotated to a position, for example, as shown in FIG. 27B,the rake assembly 222 is able to push the waste as far as possibletoward the waste end 232 of the litter tray 206. As the drive assembly218 reaches the end of travel during a forward stroke in the directionof the arrow 226 (FIG. 27B), the rake assembly 222 rotates in acounter-clockwise direction as the rake assembly 222 travels in adirection of the arrow 234 (FIG. 27C) during a reverse stroke.

Description of the Component Parts of the Alternative Embodiment ChassisAssembly

Turning to FIG. 19, the chassis assembly 216 includes a pair ofspaced-apart side rails 238, 240, connected together on the waste end232 by a front rail 242. A rear rail 244 is used to connect the siderails 238 and 240 at the home end 224 (FIG. 20). When assembled, thechassis assembly 216 forms an open bottom rectangular structure having aperimeter slightly larger than the perimeter of the litter tray 206.

Drive Assembly

The drive assembly 218 includes a pair of lead screws 246, which arecarried by the side rails 238 and 240. One end of the lead screws 246are carried by a bracket bearing 248 on the waste end 232 and a bearing250 on the opposing home end 224.

The lead screws 246 form part of the drive assembly 218. The balance ofthe drive assembly is carried by the rear rail 244. In particular, therear rail 244 carries a drive motor 252, secured to the rear rail 244,by way of a motor mount 254. A worm 256 cooperates with a worm andpulley assembly 258, to drive one lead screw 246, carried by the siderail 238. A spaced-apart pulley 260, is coupled to the other lead screw246, carried by the side rail 240.

A belt 262 is used to turn the pulley 260 and in turn, the other leadscrew 246 on the side rail 240. In one embodiment, a nut follower 264may be used to couple the rake assembly 222 to the drive assembly 218 tocause the rake assembly 222 to sweep across the litter tray 206 duringboth a forward and reverse stroke. As will be discussed in more detailbelow, the drive nut 263 and the nut follower 264 are mechanicallycoupled together by way of a tilt arm 296 (FIG. 26B) and a biasingspring 308 (FIG. 28B).

Lift Arm

Turning to FIGS. 22A-C, the lift arm 220 is used to lift the system lid204 as the rake assembly 222 approaches the waste end 232. Moreparticularly, as the nut follower 264 advances in a forward stroketowards the waste end 232, the lift arm 220 is caused to lift which, inturn, rotates the system lid 204 in a counter-clockwise direction asshown in FIGS. 22B and 22C.

As shown in FIG. 21, the lift arm 220 is configured as a lever that ispivotally-connected to the side rail 240 on one end by way of a pin 267.Rotational movement of the lift arm 220 is limited by way of another pin268 and an elongated slot 270. The elongated slot 270 receives the pin268 and allows the lift arm 220 to rotate along an arcuate path definedby the slot 270. The lift arm 220 also includes an inwardly projectingpin 272. The pin 272 cooperates with a cam surface 278 (FIG. 22A) formedon the underside of the system lid 204 and is used to control thelifting of the system lid:

As shown in FIGS. 22A-C, as the nut follower 264 advances towards thewaste end 232, the lift arm 220 rotates in a clockwise direction causingthe system lid 204 to lift and rotate in a counter-clockwise direction.In particular, one portion of the lift arm 220 is formed with a camsurface 274 The cam surface 274 on the lift arm 220 is adapted to engagea cam surface 276 on the nut follower 264. Thus, as the nut follower 264moves in a direction of the arrow 226 (FIG. 20), the cam surface 276 onthe nut follower 264 engages the cam surface 274 on the lift arm 220causing the lift arm 220 to lift as shown in FIGS. 22B and 22C. The camsurface 274 is shaped to provide a constant rate of lift as the nutfollower 264 traverses. As the nut follower 264 continues to move in thedirection of the arrow 226 (FIG. 20), the pin 272 advances along the camsurface 278 formed on the underside of the system lid 204. As the nutfollower 264 continues to move further in the direction of the arrow226, the lift arm 220 continues moving upwardly, which causes the systemlid 204 to rotate in a counter-clockwise direction. As the nut follower264 gets to its end of travel during a forward stroke, the lift arm 220continues to lift, thereby causing the system lid 204 to rotate in acounter-clockwise direction. Since the system lid 204 is magnetically orotherwise mechanically coupled to the tray lid 228, lifting of thesystem lid also causes lifting of the tray lid 228, as best shown inFIG. 27B. As the nut follower 264 reaches its end of travel positionduring a forward stroke, an “end” limit switch is tripped, which asdiscussed below, results in the direction of rotation of the drive motor252 being reversed. After the direction of the drive motor 252 isreversed, the drive nut 263 reverses direction and travels in thedirection of the arrow 234 (FIG. 20) during a return stroke (i.e. fromthe waste end 232 to the home position 224). When the drive nut 263reverses direction (I.e. travels in a direction of the arrow 234), thenut follower 264 will also reverse direction because of the mechanicalcoupling there between, resulting in the lift arm 220 dropping down toits initial position as shown in FIG. 22A, which, in turn, causes thesystem lid 204 and the tray lid 228 to rotate back to its initialposition as shown in FIG. 22A. Continued movement of the nut follower264 during a return stroke causes a disengagement of the cam surface 276of the nut follower 264 from the cam surface 274 of the lift arm 220.

Rake Assembly

The rake assembly 222 is best shown in FIG. 19. As shown, the rakeassembly 222 includes a plurality of tines 284 rigidly secured to a wireframe 286. The wire frame 286 includes a pair of vertical legs 288 and290. As shown in FIG. 21, for example, the vertical legs 288 and 290 arepivotally coupled to the nut followers 264 on each side of theself-cleaning litter box 200 at a pivot 294 (FIG. 25B). The pivot point294 allows the rake assembly 222 to pivot about a vertical axis 223(FIGS. 27A and 27D) plus and minus θ° , for example, plus or minus 45°.In particular, by pivoting the rake assembly 222 at the bottom of therake assembly 222, linear movement of the rake assembly 222 through thelitter causes the rake assembly 222 to pivot, for example plus 45°,during a return stroke 234, as generally shown in FIGS. 27C and 27D, andminus 45°, for example, during a forward stroke 226 relative to avertical axis 223, as shown in FIGS. 27A and 27B. The amount of rotationis limited by the contact of the rake assembly 222 with the tops of theside rails 238 and 240. Thus, as the rake assembly 222 changesdirections, as shown in FIGS. 27B and 27C, the rake assembly 222 flipspositions. The rake assembly 222 can also be made to flip atpre-determined locations as seen fit for functional requirements byintroducing a resistance anywhere above the pivot point along the lengthof travel. The configuration of the tines 284 may be as otherwisedescribed above.

The importance of backward angle of the rake tines with respect totravel direction for large size litter such as crystal litter is that iteliminates the wave in front of the rake assembly thus allowing theself-cleaning litter box to be used with crystal litter. Anotherimportant benefit of the self flipping rake design is that the rakeautomatically reverses angle with a change in rake travel direction.This action facilitates raking in both directions, increasing the degreeof litter mixing. With better litter mixing, the litter absorbs urineodor better and lasts longer, permitting a longer period of operationbefore user intervention. Furthermore, the self flipping rakedistributes litter evenly in both rake travel directions, preventing abias of litter to one end of the litter cartridge over time.Furthermore, bi-directional raking with the tines fully disposed intothe litter redistributes and levels the litter bed after a cat hasdisturbed the litter bed by digging and piling of the litternon-uniformly.

Drive Nut and Drive Follower

As mentioned above, the drive assembly 218 (FIG. 19) includes a pair oflead screws 246. The drive assembly 218 also includes a worm 256 coupledto the shaft (not shown) of the motor 252. The worm 256 cooperates witha worm gear 258 which may be either integrally formed or directlycoupled to a pulley 258 that is directly coupled to one lead screw 246.A second pulley 260 is directly coupled to the other lead screw 246. Abelt 262 couples the two pulleys 258 and 260. A tension arm 291 andtension pulley 292 (FIG. 17) may be used to keep tension in the belt262. The lead screws 246 are used to drive a drive nut 263 and themechanically coupled nut follower 264.

As the drive motor 252 (FIG. 19) is energized, the rotation of the drivemotor 252 causes rotation of worm 256 and the worm gear 258, which, inturn, drives one lead screw 246 and the pulley 258. The pulley 258drives the pulley 260 by way of the belt 262. Rotation of the pulleys258, 260 causes rotation of the other lead screw 246. As the lead screws246 rotate in a forward direction, the drive nut 263 and the nutfollower 264 advance towards the waste end 232 during a forward stroke.As the lead screws 246 rotate in a reverse direction, the drive nut 262and nut follower 263 travel in reverse in a return stroke back to a homeposition.

As shown in FIG. 23A, the vertical legs 288 and 290 of the rake assembly222 are pivotally-connected to the nut follower 264 at one end by way ofa pivot 294. A tilt arm 296 is pivotally-connected to the drive nut 263by way of a pivot 298. The tilt arm 296 is used to disengage nutfollower 264 from the drive nut 263, which in turn disconnects the rakeassembly 222 from the drive nut 263 as shown in FIGS. 23A-D. The tiltarm 296 includes a hook 300 which cooperates with a cam surface 302,formed in the nut follower 264. More particularly, as shown in FIG. 23A,the hook 300 on the tilt arm 296 engages the cam surface 302 on the nutfollower 264 in a normal position to drive the rake assembly 222, forexample, as shown in FIG. 23A. As mentioned above, as the drive nut 263approaches its end of travel in the home position 224 (FIG. 20). A rampon the tilt arm 296 engages a stop on the side rail and causes the tiltarm 296 to rotate in a clockwise direction, as shown in FIG. 23B. Theclockwise rotation of the tilt arm 296 causes the hook 300 to disengagefrom the cam surface 302 on the tilt arm 296, as shown. As shown in FIG.23B, a stop 304, formed in the side rail 240 stops further linear travelof the nut follower 264. Continued rotation of the lead screw 246 causesfurther advancement of the drive nut 263 as well as the tilt arm 296towards the home position. A pin 306, formed on one end of the tilt arm296 engages one of the vertical legs 290 of the rake assembly 222 tocause it to rotate in a clockwise direction. Continued movement of thedrive nut 263 in a direction of the arrow 234 (FIG. 20) causes the drivenut 263 to advance further to the right, as shown in FIG. 23C. Thisaction allows the rake assembly 222 to stop linear travel and thenrotate, minimizing the forces required to place the rake assembly in ahome position and reducing the collection of litter behind the rake inthe home position A biasing spring 308 that connects the nut follower264 to the drive nut 263 is biased as the drive nut 263 gets to its endof travel, as shown in FIG. 23C. When the cycle is repeated (i.e., aforward stroke is again initiated), the tension in the biasing spring308 causes the hook 300 to latch into cam surface 302 of the tilt arm296.

Flip Arm

An alternative embodiment of the drive assembly 218 is illustrated inFIGS. 24A-C. In this embodiment, the drive assembly 218 includes a drivenut 267 (without a corresponding nut follower) and a flip arm 309 inlieu of the drive nut 263 and nut follower 264 illustrated, for example,in FIG. 23A. In this embodiment, the vertical legs 288, 290 of the rakeassembly 222 are pivotally connected to the drive nut 267 at a pivotpoint 269. The flip arm 309 is pivotally-connected to the drive nut 267about a pivot point 312 (FIG. 24A). The flip arm 309, formed as anL-shaped member with a pin 314 formed on one end. During a returnstroke, the vertical leg 290 of the rake assembly rests against the pin314. A stop 316, formed in the side rail 240, engages one end of theflip arm 309. Continued movement in the direction of the return strokecauses the flip arm 309 to rotate about the pivot axis 312. This causesthe flip arm 309 to rotate in a clockwise direction. Rotation of theflip arm 309 in a clockwise direction causes the pin 314 to engage thevertical leg 290 of the rake assembly to cause it also to move in aclockwise direction to force the rake assembly to a park position asgenerally shown in FIG. 31A. The flip arm 309 does not stop lineartravel of the rake assembly 222 while the rake assembly 222 rotates.

Controller

The controller for the self-cleaning litter box 200 is illustrated inFIG. 25 and generally identified with the reference numeral 310. Thecontroller 310 includes a microprocessor 311, for example, and a modelATTINY26-SC. The controller 310 includes a motor drive circuit 312 whichdrives the drive motor 252 in a first direction during a forward strokeand a reverse direction during a return stroke. The motor controller 312includes a plurality of transistors Q1, Q2, Q3, Q4, Q6, and Q7. Inaddition, the motor controller circuit 312 also includes a plurality ofdiodes D2, D3, D5, D6, resistors R7, R8, R10, R11, R13, R14, R15, R19,R20, R21, and capacitors C10 and C11. The transistors Q1, Q3 and Q7control DC power to the motor in one direction while the transistors Q2,Q4 and Q6 control DC power to the drive motor 252 in a reversedirection. More particularly, the transistors Q1 and Q2 are normallyopen. At power-up, the signals; MOTOR_OUT_1, MOTOR_OUT_2, MOTOR_OUT_3and MOTOR_OUT_4 are all low resulting in the drive transistors Q1-Q7 allbeing off. Also, the drive motor 252 may be stopped by causing the drivesignals; MOTOR_OUT_1, MOTOR_OUT_2, MOTOR_OUT_3 and MOTOR_OUT_4 to golow.

The diodes D2, D3, D5, and D6 provide full wave rectification of themotor supply voltage HV_IN. In particular, the diodes D2, D3, D5, and D6produce a + supply voltage at the node between the diodes D2 and D5 and0 volts at the node between the diodes D3 and D6.

In a forward direction, the drive signals MOTOR_OUT_1 and MOTOR_OUT_4 gohigh. The high MOTOR_OUT_1 signal causes the transistor Q3 to close,which, in turn, causes the transistor Q1 to close. When the transistorQ1 switches closed, the supply voltage for the drive motor 252 isconnected to a MOTOR_OUT_A terminal and 0 volts on a MOTOR_OUT_Bterminal, which in turn are connected to the drive motor 252.

In a reverse direction, the signals MOTOR_OUT_2 and MOTOR_OUT_3 go high.The high MOTOR_OUT_2 signal causes the drive transistor Q4 to close,which in turn causes the drive transistor Q2 to close. This causes apositive supply voltage to be connected to the motor terminalMOTOR_OUT_B, by way of the transistor Q2. The high MOTOR_OUT_3 signalcauses the drive transistor Q6 to close which connects 0 volts to themotor terminal MOTOR_A.

Irrespective of the direction of rotation of the drive motor 252, themotor drive current is sensed by a current sense circuit 312 whichincludes plurality of current sense resistors R35, R32, connected inparallel as shown. These current sense resistors are R35-R42 form avoltage divider with a resistor R23, which, in turn, is connected to aninverting input of a comparator 314. A reference voltage is applied tothe non-inverting input of the comparator 314. The reference voltage isdeveloped by a +5 volt DC source in a voltage divider formed from theresistors R28 and R29. A bypass capacitor C4 may be coupled to theinverting input of the comparator 314 to stabilize the output. Theoutput of the comparator 314 is pulled high by way of a pull-up resistorR26. The output of the comparator 314 is normally high and is sensed bya PB6/INTO of the microprocessor 311. Whenever the motor drive currentexceeds a predetermined value, for example, 550 milli-amps, the voltageapplied to the inverting input will be high enough to trigger comparator314, indicating a locked rotor condition for a predetermined time,indicative, for example, that the rake assembly 222 is stuck and thedrive motor 252 is in a locked rotor condition, indicating a cat may beblocking the rake assembly 222. The trip set point of the comparator 314is determined by the resistors R28 and R32. When the comparator 314 istriggered, its output goes low. This low signal CUR_LIM_IN is applied tothe microprocessor 311 which shuts off whichever of the drive signalsMOTOR_OUT_3 or MOTOR_OUT_4 that is high and re-enables the signal after,for example 250 microseconds. If a 550 milliampere condition persistsfor a predetermined time period, for example, 200 milliseconds, thedrive motor 252 is assumed to be stalled and it is shut off.

The controller 310 also includes an infrared (IR) circuit detector, usedto detect the presence of a cat in a self-cleaning litter box 200. TheIR detector circuit includes an infrared diode (not shown), aphoto-transistor (not shown) a transistor Q5, a pair of current limitingresistors R9 and R12, a comparator 316, a plurality of resistors R27,R34, R31, R33, R25, and R30. Power is constantly supplied to theinfrared diode and photo-transistor by way of the five-volt power supplyand a resistor R2 at a terminal IR_OUT_1 (pin 8 of the connector J1).

An infrared sensor control signal IR_LED_OUT is normally low.Periodically, this infrared sensor control signal IR_LED_OUT goes highfor example for 10 microseconds, to turn on the transistor Q5. Thiscauses a relatively large current, for example >250 milliamps to flowthrough the IR diode(not shown) by way of the terminal IR_OUT_2. Thiscauses the IR diode to flash, which, in turn, is detected by aphoto-transistor (not shown) connected to pin 5 of the connector J1. Theoutput of the photo-transistor is a pulse signal IR_SENSE_IN that isconnected to a terminal 5 on a connector 317 and applied to anon-inverting input of a comparator 316. When the beam is not broken,indicating the absence of a cat, the non-inverting input is pulled lowtripping the comparator 316 causing the comparator output 316 to go low.After the IR_SENSE_IN pulse passes (i.e. the photo-transistor isshut-off), the non-inverting input of the comparator 314 goes high whichcauses the voltage on the capacitor C6 to float back to its nominallevel, resulting in the comparator 316 returning to a high state.)

The microprocessor 311 continuously monitors the IR detector activityeven while the drive motor 252 is running. If the microprocessor 311continuously receives the IR_SENSE_IN pulses, then the system assumesthat the beam is not broken. If no pulses are received, for example, 3or more time periods, the beam is considered to be broken indicatingthat a cat is in the litter box.

There are also two other system inputs to the microcontroller 311. Inparticular, there are two limit switches, identified as an “end” limitswitch at the waste end 232 and a “home” limit switch at the homeposition 224. These limit switch inputs are applied to pins 1 and 3 ofthe connector 37 and, in turn, to the microprocessor 311 ports PB3 andPB4/XTAL1. These inputs are pulled up by way of pull-up resistors R16and R17. The limit switches are used to provide a signal to themicrocontroller 311 to stop the drive motor 252 at the end of theforward cycle and to reverse its direction. The system may also includean optional cycle switch S1 which allows the rake assembly 222 and driveassembly 218 to cycle through one cycle of operation. The cycle switchis coupled to a port PA1/ADC1 of the microcontroller 311. The cycleswitch is pulled high by a pull-up resistor R1.

Power for the circuit is developed by a power supply 319. For example, anational semiconductor, model no. LM78M05CT. Bypass capacitors C10 andC11 can be used to optionally stabilize the power supply.

An LED 320 may be provided to indicate various states in the rakingcycle as discussed below. The LED 320 is connected to a port PA2/ADC2 byway of a current-limiting resistor R12.

The logic diagram for the controller 310 is illustrated in FIG. 26.Initially, the system checks initially in step 350 to determine whetherthe cycle switch S1 has been depressed. If so, the system flashes theLED 320 at 8 Hz. in step 352 and cycles back to step 350. If the cycleswitch S1 has not been depressed, the system next checks in step 353 todetermine whether the “home” limit switch is open, indicating that thenut follower 264 has reached the home position 224. If so, the LED 320is turned on solid in step 354. The system next checks in step 356 todetermine whether the infrared beam is broken. If not, the LED 320 isturned on solid in step 358 and the system proceeds to step 360 todetermine if the cycle switch S1 has been depressed. If the cycle switchS1 has not been depressed, the system loops back to step 356. If thecycle switch has been pressed, the system initiates a cycle as discussedbelow. If the infrared beam has been broken, the LED 320 is flashed at asecond flashing rate in step 362. The system then measures the timesince the infrared beam has been broken in step 364. If less than threeseconds have elapsed, the system loops back to step 356. If more, thanthree seconds have elapsed, the system proceeds to step 366 and flashesthe LED 320 at 4 Hz. The system then checks in step 368 to determine ifthe infrared beam is clear, if not, it loops back to step 366 andcontinues flashing the LED 320 at 4 Hz. If the infrared beam is clear,the system resets the timer in step 370 and proceeds to step 372 tocheck again if the infrared beam has been broken. If so, the LED 320 isflashed at a rate of 4 Hz in step 374 and the system loops back to step370. If the infrared beam has not been broken, as determined in step372, the system flashes the LED at 1 Hz in step 376. The system thenchecks the timer to see whether more than a predetermined time period,such as 20 minutes have elapsed in step 378. If so, the system initiatesa cleaning cycle as will be discussed below. If not, the system proceedsto step 380 and checks whether the cycle switch S1 has been depressed.If so, the system loops back to step 354. If the cycle switch S1 has notbeen depressed, the system loops back to step 372.

Any time a cleaning cycle is initiated, the microprocessor 311 runs thedriver motor 252 in a forward direction by generating the signal'sMOTOR_OUT1 or MOTOR_OUT_2 to close the transistor Q1 or Q7 in step 382.After the drive motor 252 is driven forward in step 382, the LED 320 isflashed at a 1 Hz rate in step 384. The system next checks in step 386to determine whether the cycle switch S1 is down. If so, the systemexits the cleaning cycle and proceeds to step 388 and stops the motor.If the cycle switch S1 has not been depressed, the system next checks instep 390 to determine if a stalled motor condition has occurred asdiscussed above. If so, the system stops the motor in step 388. If astalled motor condition is not detected in step 390, the system checksin step 392 to determine whether the waste end limit switch is openindicating that the drive assembly 218 and rake assembly 222 has arrivedat the end of the forward stroke. If not, the system continues runningthe loops back to step 382 and continues running the drive motor 252. Ifthe waste end limit switch is open, the system stops the motor in step394 and pauses for a predetermined time period, for example, one secondand 396. Subsequently, the system reverses directions of the drive motor252 by causing the appropriate MOTOR_OUT_1 and MOTOR_OUT_3 to go low andthe signals MOTOR_OUT_2 and MOTOR_OUT_4 to go high. As discussed above,this causes the transistors Q2 and Q6 to close, which reverses thedirection of the drive motor 252 in step 398. After the drive, motor 252is being driven in a reverse direction (i.e., in a return stroke), theLED 320 is flashed at a 1 Hz rate in step 400. The system then checks instep 402 to determine whether the cycle switch S1 has been depressed. Ifso, the system stops the motor in step 388. If the system determinesthat the cycle switch S1 is not down in step 402, a stalled motorcondition is checked in step 404. If a stalled motor condition isdetected in step 404, as discussed above, the drive motor 252 is stoppedin step 388. If no stop motor condition is detected in step 404, thesystem checks in step 406 to determine whether the “home” limit switchis open. Indicating that the drive assembly 218 and rake assembly 222has returned to the home position 224. If not, the system loops back tostep 398 and continues running the drive motor 252 in a reversedirection. If the home limit switch is open, the motor is stopped instep 408 and the system pauses for a predetermined time period, forexample, one second in 410. The system then loops back to step 354.

After the motor is stopped in step 388, the LED 320 is flashed at an 8Hz rate in step 412. Subsequently, the system checks to determinewhether the cycle switch S1 is down in step 414. If not, the systemloops back to step 388. If so, the system loops back to step 398 andcycles the drive motor 252 in a reverse direction.

The signals IPS_MOSI, ISP_RST, ISP_SCK, and ISP_MISO may be used toinitially program the controller 310. These signals IPS_MOSI, ISP_RST,ISP_SCK, and ISP_MISO are external programming signals applied to aconnector JP1 and pulled high by a plurality of pull-up resistors R3,R4, R5 and R6 and applied to ports P01, P02, P03 and P04, respectively,of the microcontroller 311. The connector JP1 as well as the pull-upresistors R3, R4, R5 and R6 are only required for initial programming ofthe controller 310 and are not required for commercial embodiments sincethe system will be pre-programmed. Obviously, many modifications andvariations of the present invention are possible in light of the aboveteachings. Thus, it is to be understood that, within the scope of theappended claims, the invention may be practiced otherwise than asspecifically described above.

1-154. (canceled)
 155. A method for treating animal waste in a litterbox, comprising the steps of: periodically raking a crystal litter in aremovable single chamber tray to collect solid waste at one end of thetray; moving the rake away from the one end of the tray; and coveringthe collected solid waste at the one end of the tray. 156-157.(canceled)
 158. A method for treating animal waste in a litter box,comprising the steps of: filling a removable tray with a predeterminedcrystal litter; receiving liquid and solid animal waste into a crystallitter within the tray; absorbing the liquid waste into the crystallitter; periodically raking the crystal litter to move the solid wasteinto one area of the tray; keeping the solid waste in contact with thecrystal litter; covering the collected solid waste in the one area; andevaporating water from the crystal litter into the environment. 159-171.(canceled)
 172. A method for handling cat litter comprising the stepsof: providing a cartridge pre-filled with new litter; installing thecartridge in a litter box machine; raking cat waste to one end of thecartridge; removing the cartridge from the litter box machine; anddisposing of the cartridge containing used litter and waste.